Resin compositions, production process thereof, and products using the resin compositions

ABSTRACT

A resin composition comprises 100 parts by weight of an ethylene-base resin comprising at least 2 wt. % of linear low-density polyethylene and 0.1-30 parts by weight of an organopolysiloxane having an average molecular weight of at least 100,000. The resin composition can be produced by melting and kneading the organopolysiloxane together with the linear low-density polyethylene and then melting and kneading the resulting polymer blend together with the ethylene-base resin other than the linear low-density polyethylene. The resin composition may additionally comprise 0.1-100 parts by weight of a propylene-base resin. In the latter resin composition, the organopolysiloxane is contained in an amount of 0.1-30 parts by weight per 100 parts by weight of the sum of the ethylene-base resin and the propylene-base resin. The latter resin composition can be produced by melting and kneading the organopolysiloxane together with the propylene-base resin and then melting and kneading the resulting polymer blend together with the ethylene-base resin. Optical fiber feeding pipes and optical fiber units making use of such resin compositions are also described.

This is a divisional application of Ser. No. 08/117,701, filed Sep. 8,1993, now abandoned.

BACKGROUND OF THE INVENTION

1) Field of the Invention

This invention relates to novel resin compositions having excellentsurface lubricity, and more specifically to resin compositions havingextremely good surface lubricity and also superb abrasion resistance andmechanical strength. Further, this invention is concerned with a processfor the production of the resin compositions and also with productsusing the resin compositions.

2) Description of the Related Art

Resin composition s having excellent surface lubricity have foundutility as mechanical parts such as gears, cams and levers, pipes fortransporting materials or articles such as pressurized air carryingoptical fiber feeding pipes, and sliding members such as guide rollers.

As a conventional method for improving the surface lubricity of a moldedor otherwise formed resin body (hereinafter collectively called the"formed body"), it is known as the simplest method to coat the surfaceof the formed body with silicone oil as a lubricant.

Such a conventional method is however accompanied by the problem thatthe silicone oil present on the surface of the formed body is graduallylost through contact with other objects and lubricating effect of thesilicone oil does not last over a long period. The conventional methodinvolves the additional problem that the objects so contacted aresmeared with the silicone oil.

With a view toward overcoming the problems described above, a processhas been proposed to obtain a formed body by using a resin compositionwith a lubricant component such as silicone oil mixed in a resin.

The formed body obtained from the resin composition, which contains thelubricant component incorporated in the resin, has a certain degree oflubricity. To allow the formed body to exhibit a high degree oflubricity, however, addition of a great deal of silicone oil is needed,leading to problems such that the resulting resin composition showsreduced formability or moldability and can provide only formed bodies ofreduced mechanical strength. Even if lubricity can be imparted to apossible maximum degree at the sacrifice of mechanical strength, thelubricity so attained is still not fully satisfactory for theabove-described applications.

SUMMARY OF THE INVENTION

There is accordingly a desire for the development of a resin compositionwhich has a high degree of lubricity and excellent mechanical strengthin view of the above-described various applications.

To overcome the above-described problems, the present inventors haveproceeded with extensive research on the development of lubricitythrough combinations of lubricant components and resins.

As a result, it has been found that a combination of an ethylene-baseresin containing linear low-density polyethylene in a specific amountand a polyorganosiloxane having a particular molecular weight canprovide a resin composition capable of furnishing a formed body havingnot only significantly improved surface lubricity but also excellentabrasion resistance and mechanical strength, leading to the completionof the present invention.

In one aspect of the present invention, there is thus provided a resincomposition comprising:

100 parts by weight of an ethylene-base resin comprising at least 2 wt.% of linear low-density polyethylene; and

0.1-30 parts by weight of an organopolysiloxane having an averagemolecular weight of at least 100,000.

In another aspect of the present invention, there is also provided aresin composition comprising:

100 parts by weight of an ethylene-base resin comprising at least 2 wt.% of linear low-density polyethylene;

0.1-100 parts by weight of a propylene-base resin; and

0.1-30 parts by weight, per 100 parts by weight of the sum of theethylene-base resin and the propylene-base resin, of anorganopolysiloxane having an average molecular weight of at least100,000.

In a further aspect of this invention, there is also provided a processfor the production of the former resin composition, which comprises:

melting and kneading the organopolysiloxane together with the linearlow-density polyethylene; and

melting and kneading the resulting polymer blend together with theethylene-base resin other than the linear low-density polyethylene insuch proportions that the resulting resin composition comprises 100parts by weight of the ethylene-base resin comprising at least 2 wt. %of the linear low-density polyethylene and 0.1-30 parts by weight of theorganopolysiloxane having an average molecular weight of at least100,000.

In a still further aspect of the present invention, there is alsoprovided a process for the production of the latter resin composition,which comprises:

melting and kneading the organopolysiloxane together with thepropylene-base resin; and

melting and kneading the resulting polymer blend together with theethylene-base resin, which comprises at least 2 wt. % of the linearlow-density polyethylene, in such proportions that the resulting resincomposition comprises 100 parts by weight of the ethylene-base resincomprising at least 2 wt. % of linear low-density polyethylene, 0.1-100parts by weight of the propylene-base resin and 0.1-30 parts by weight,per 100 parts by weight of the sum of the ethylene-base resin and thepropylene-base resin, of the organopolysiloxane.

In a still further aspect of the present invention, there is alsoprovided an optical fiber feeding pipe comprising a layer of the formeror latter resin composition formed on at least an inner wall thereof.

In a still further aspect of the present invention, there is alsoprovided an optical fiber unit comprising a layer of the former orlatter resin composition formed on at least an outermost layer thereof.

The resin compositions according to the present invention can provide,owing to the addition of the organopolysiloxane in the small amount,formed bodies having not only excellent surface lubricity but alsosuperb abrasion resistance and mechanical strength.

The resin compositions of this invention can therefore be used in a widevariety of applications making use of such properties, for example,mechanical parts such as gears, cams and levers, pipes for transportingmaterials or articles such as pressurized air carrying optical fiberfeeding pipes, coating materials for optical fiber units, and slidingmembers such as guide rollers.

In particular, optical fiber feeding pipes of the pressurized-aircarrying type having a layer of one of the resin compositions accordingto this invention on at least inner walls thereof are excellent insurface lubricity so that they permit pressurized-air carrying of anoptical fiber over a long distance irrespective of the coating materialor surface condition of the optical fiber unit to be inserted underpressure and also irrespective of the state of installation of the pipeitself.

In optical fiber units having a coating layer made of one of the resincompositions according to the present invention on at least outermostlayers thereof, their surfaces show excellent lubricity so that they canbe fed under pressure through feeding pipes over a long distanceirrespective of the material or the like of the feeding pipes.

Further, optical fiber feeding pipes and optical fiber units producedusing one of the resin compositions according to this invention areexcellent in surface lubricity, thereby making it possible, differentfrom the prior art, to insert optical fiber units by the suction methodor the push method even in subscribers--loops or buildings where theoptical fibers are bent frequently although the distances of insertionare relatively short. It is therefore unnecessary to use specialequipment, thereby bringing about the advantageous effect that on-siteinstallation work becomes extremely easy.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENT

The technical features of the present invention will hereinafter bedescribed in detail.

In the present invention, it is important to use, as a resin, anethylene-base resin containing at least 2 wt. %, especially 5 wt. % ormore of linear low-density polyethylene, because the present inventionis based on the finding that extremely high lubricity can be exhibitedwhen an organopolysiloxane of an extremely high molecular weight, whichis to be described subsequently, is added to an ethylene-base resin.

As a result of research conducted by the present inventors with a viewto determining a resin which makes it possible to draw the lubricity ofan organo-polysiloxane to a maximum extent when combined with theorganopolysiloxane, it was found that an ethylene-base resin iseffective as such a resin and also that inclusion of linear low-densitypolyethylene in a particular amount or more in the ethylene-base resinpermits high-degree dispersion of the organopolysiloxane and addition ofthe organopolysiloxane in a small amount can therefore significantlyimprove the lubricity without lowering the strength of the resultingformed resin body.

If an ethylene-base resin containing linear low-density polyethylene inan amount smaller than 2 wt. % is used, it is difficult to disperse thehigh molecular weight organopolysiloxane to a high degree in the resinso that the objects of the present invention cannot be achieved.

No particular limitation is imposed on the proportion of the linearlow-density polyethylene in the ethylene-base resin. The ethylene-baseresin may therefore be formed entirely of linear low-densitypolyethylene. To control physical properties, such as hardness andmechanical strength, of the resulting resin composition, however,another ethylene-base resin composed predominantly of ethylene can becontained, as needed, within the range described above.

In the present invention, conventional linear low-density polyethyleneresins available by copolymerizing ethylene with α-olefins such asbutene-1 can be used as the linear low-density polyethylene without anyparticular limitation. These linear low-density polyethylene resinsgenerally have a density in a range of from 0.910 to 0.925. Among these,those having an average molecular weight ranging from 10,000 to 200,000can be suitably used in the present invention.

As the ethylene-base resin, any known ethylene-base resins can be usedin the present invention without any particular limitation insofar asthey contain the above-described linear low-density polyethylene and arecomposed predominantly of ethylene having good compatibility with thelinear low-density polyethylene. Illustrative ethylene-base resinsinclude homopolymers such as low-density polyethylene and copolymerscomposed primarily of ethylene. Of these, high-density polyethylenehaving a high crystallization degree is particularly preferred as it canfurther enhance the lubricity-improving effect of the resulting resincomposition.

In the present invention, preferred examples of the ethylene-base resinare those formed of 2-50 wt. %, preferably 5-30 wt. % of linearlow-density polyethylene and the remainder of an ethylene-base resinother than linear low-density polyethylene, especially high-densitypolyethylene.

To further improve the dispersibility of the organopolysiloxane into theethylene-base resin and also to improve the lubricity of the resultingresin composition, it is preferred to add a propylene-base resin in anamount of 0.1-100 parts by weight, preferably 0.3-20 parts by weight,more preferably 0.3-10 parts by weight per 100 parts by weight of theethylene-base resin in the present invention. The propylene-base resinexhibits its effects when added in an amount of 0.1 part by weight ormore. Amounts greater than 100 parts by weight however tend to suppressthe lubricity-imparting effect derived under the action of theethylene-base resin and the organopolysiloxane and to reduce thelubricity conversely.

Any known propylene-base resin formed primarily of propylene can be usedas the propylene-base resin without any particular limitation.

Usable exemplary propylene-base resins include propylene homopolymer;copolymers such as block copolymers, random copolymers and graftcopolymers of propylene and α-olefins other than propylene, such asethylene and butene-1; and mixtures thereof. Of these copolymers, thosecontaining ethylene units in a range not greater than 30 mole %, morepreferably 0.15-15 mole % are particularly preferred.

Illustrative of the organopolysiloxane employed in the present inventioninclude those having an average molecular weight of at least 100,000,preferably those having a high molecular weight of from 300,000 to5,000,000. If the average molecular weight of an organopolysiloxane issmaller than 100,000, the organopolysiloxane does not have sufficientlubricity-improving effect so that the objects of the present inventioncannot be achieved.

Organopolysiloxanes of any known structure can be used without anyparticular limitation provided that they have the molecular weightspecified above.

Usable organopolysiloxanes include, for example, dimethylpolysiloxane,methylphenylpolysiloxane and ethylhydrogenpolysiloxane as well asmodified organopolysiloxanes such as those obtained by subjecting theabove-mentioned polysiloxanes to modifications such as alkylmodification, amino modification, epoxy modification, mercaptomodification, chloroalkyl modification, alcohol modification, polyethermodification and fluorine modification.

Incidentally, the organopolysiloxane employed in the present inventioncan be either linear or branched.

The amount of the organopolysiloxane added in the present invention is0.1-30 parts by weight, preferably 0.3-20 parts by weight per 100 partsby weight of the ethylene-base resin or the sum of the ethylene-baseresin and the propylene-base resin.

Amounts less than 0.1 part by weight are too small to sufficientlyimprove the lubricity. Amounts greater than 30 parts by weight, on theother hand, cannot bring about additional lubricating effect. Use of theorganopolysiloxane in such unduly large amounts are thereforedisadvantageous from the economical standpoint and, moreover, tend toreduce physical properties such as mechanical strength.

In the present invention, the organopolysiloxane can be dispersed in aform merely mixed in the ethylene-base resin or in the ethylene-baseresin and propylene-base resin or can be partly grafted with the resin.

Needless to say, the resin composition according to the presentinvention can be added with known additives such as anitoxidants, lightstabilizers, antistatic agents, pigments and fillers to an extent notsignificantly deteriorating the effects of the present invention such aslubricity.

Although no particular limitation is imposed on the process for theproduction of the resin composition of this invention, it is preferredto adopt such a process that an organopolysiloxane having a highmolecular weight of 100,000 or higher in terms of average molecularweight can be dispersed to a high degree in an ethylene-base resin whichcontains at least 2 wt. % of linear low-density polyethylene.

The resin composition can be produced generally by melting and kneadingthe organopolysiloxane with the linear low-density polyethylene havingrelatively good compatibility with the organopolysiloxane and, ifnecessary, melting and kneading the resulting blend and the remainder ofthe ethylene-base resin so that the resin composition comprises 100parts by weight of the ethylene-base resin containing at least 2 wt. %of linear low-density polyethylene and 0.1-30 parts by weight of theorganopolysiloxane having an average molecular weight of 100,000 orhigher.

Any known method can be adopted without any particular limitation forthe above-described melting and kneading. In general, the melting andkneading can be carried out at 160°-300° C., preferably 180°-270° C. byusing a mixer such as a screw extruder, a Banbury mixer or mixing rolls.

In the process described above, it is preferred to cause an organicperoxide to exist upon melting and kneading so that the dispersibilityof the organopolysiloxane in linear low-density polyethylene can beimproved.

No particular limitation is imposed on the organic peroxide employed inthe above process as long as it decomposes to produce radicals at themelting and kneading temperature. Examples of such organic peroxidesinclude ketone peroxides such as methyl ethyl ketone peroxide, methylisobutyl ketone peroxide and cyclohexanone peroxide; diacyl peroxidessuch as isobutyryl peroxide, lauroyl peroxide and benzoyl peroxide;hydroperoxides such as diisopropylbenzene hydroperoxide; dialkylperoxides such as dicumyl peroxide,2,5-dimethyl-2,5-di(t-butylperoxy)hexane,1,3-bis-(t-butylperoxyisopropyl)benzene, di-t-butyl peroxide, and2,5-dimethyl-2,5-di-(t-butylperoxy)hexane-3; peroxyketals such as1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane and2,2-di(5-butylperoxy)butane; alkyl peresters such as t-butylperoxypivarate and t-butyl peroxybenzoate; percarbonates such as t-butylperoxyisopropyl carbonate.

The organic peroxide can be used in an amount of 0.001-0.1 part byweight per 100 parts by weight of the resin fed upon mixing andkneading.

In the above-described production process of the resin composition ofthis invention, a propylene-base resin having still better compatibilitywith the high-molecular organopolysiloxane can be used further. Aftermixing the resin and the organopolysiloxane in advance, the resultingpolymer blend is mixed with the ethylene-base resin, thereby making itpossible to obtain a resin composition permitting still improveddispersion of the organopolysiloxane.

Namely, the above-described process comprises melting and kneading theorganopolysiloxane having the molecular weight of at least 100,000together with the propylene-base resin and then melting and kneading theresulting polymer blend together with the ethylene-base resin, whichcomprises at least 2 wt. % of the linear low-density polyethylene, insuch proportions that the resulting resin composition comprises 100parts by weight of the ethylene-base resin, 0.1-100 parts by weight ofthe propylene-base resin and 0.1-30 parts by weight, per 100 parts byweight of the sum of the ethylene-base resin and the propylene-baseresin, of the organopolysiloxane.

In the above process, a mixer similar to that described above can beused for the melting and kneading. The suitable melting and kneadingtemperature is 160°-300° C., with 180°-270° C. being preferred.

In the above process, it is preferred to cause a peroxide to existduring the melting and kneading so that the dispersibility of theorganopolysiloxane in the propylene-base resin can be improved. Noparticular limitation is imposed on an organic peroxide employed in theabove process as long as it decomposes to produce radicals at themelting and kneading temperature. As such an organic peroxide, any oneof the above-exemplified organic peroxides can be selected and used asneeded.

After the propylene-base resin and the organopolysiloxane are melted andkneaded, the resulting polymer blend is melted and kneaded with theethylene-base resin. This melting and kneading can be performed directlytogether with the ethylene-base resin containing linear low-densitypolyethylene. In particular, it is however preferred to melt and kneadthe polymer blend with the linear low-density polyethylene and then tomelt and knead the thus-formed blend with the remainder of theethylene-base resin.

In the above-described production process of the resin composition ofthis invention, the organopolysiloxanes exemplified above can be usedwithout any limitation. In particular, those containing 0.001-0.3 wt. %of vinyl groups can be used suitably.

As the above-described vinyl-containing organopolysiloxane, it isgenerally possible to use such an organopolysiloxane as produced bysetting production conditions to control the content of vinyl groups at0.001-0.3 wt. % in the molecule or as produced by replacing each organicgroup, which is bonded to a silicon atom, with a vinyl group.Organopolysiloxanes usable most suitably in the present invention arethose obtained by substituting vinyl groups for methyl groups ofdimethylpolysiloxanes having an average molecular weight of 100,000 ormore so that vinyl groups are contained within the range specifiedabove.

No particular limitation is imposed on the forming method of the resincomposition of this invention. Conventional forming methods such asextrusion and injection molding can therefore be adopted. Of these,extrusion can bring about the advantages of the present inventionmarkedly.

The resin compositions according to the present invention are excellentnot only in surface smoothness but also in abrasion resistance andmechanical strength.

Accordingly, the present invention can also provide various productsmaking use of these excellent properties.

The resin compositions according to the present invention are henceuseful, for example, as mechanical parts such as gears, cams and levers,sliding members such as guide rollers, and optical-fiber-relatedproducts requiring high surface lubricity, more specifically,pressurized air carrying optical fiber feeding pipes and coatingmaterials for optical fiber units.

A detailed description will next be made of the extremely highusefulness of the above resin composition of this invention foroptical-fiber-related products among the products making use of theresin composition according to this invention.

As is known well, pressurized air carrying optical fiber feeding pipesare installed in a form assembled beforehand in cables such as powercables or optical fiber cables to meet any future increase in the demandfor optical transmission lines. At the time of such an increase indemand, the demand increase can be appropriately coped with by feedingpressurized gas such as air into the optical fiber feeding pipes andinserting cables such as optical fiber units into the optical fiberfeeding pipes.

As has been described above, optical transmission lines installed in theair or ground or in a building are provided with a special pipe capableof introducing an optical fiber unit into the cable in advance so thatadditional optical fibers can be installed to meet a future increase inthe volume of transmission or the optical fibers can be replaced byfresh optical fibers as a result of quality improvements in opticalfibers.

To insert an optical fiber unit or the like into such a special pipe asdescribed above, a pressurized air carrying method making use ofcompressed air or the like, which is called the "streaming method", isgenerally adopted. According to this method, the optical fiber unit orthe like to be inserted is fed by rollers or the like and, at the sametime, compressed gas is blown into the special pipe so that the opticalfiber or the like is allowed to advance while being carried by the gasstream.

In the above-described insertion of the optical fiber unit or the likeby the pressurize air carrying method, there is a limitation to thedistance of pressure feeding, in other words, the problem that theoptical fiber unit or the like cannot be pressure fed over a longdistance where the coefficient of friction between the inserted opticalfiber and the pipe is high. Further, the distance of pressure feedingvaries depending on whether the state of installation of a pipe isstraight or curved, leading to the problem that the optical fiber unitor the like may not be pressure fed over a desired distance in someinstances.

To overcome such problems, it has heretofore been the practice to employone or more of the following methods:

(1) A distance of pressure feeding is divided into short sections.Optical fibers are inserted through the respective sections and are thenconnected.

(2) As a resin composition for pipes, a resin composition added with anamide-base lubricant is used.

(3) To reduce the friction of coefficient, the inner wall of a pipe iscoated with a lubricant.

The method (1) however involves a transmission loss due to theconnection, leading to the problem that long-distance transmissionrequires repeaters or amplifiers. According to the method (2), theeffect of the amide-base lubricant does not last long. Moreover, theresulting pipe is sensitive to temperature variations and cannot stablyprovide constant lubricity.

The method (3), on the other hand, is effective in substantiallyincreasing the distance of pressure feeding irrespective of the state ofinstallation, that is, no matter whether the pipe is installed in alinear state or in a curved state. Compared with a pipe not coated withany lubricant, pressure feeding over a distance 2-3 times as much as ageneral feeding distance namely, up to about 1,000 m is feasible.

The method (3) is however accompanied by the practical problem thatcoating of the lubricant inside a pipe is difficult where the pipe has alarge length. Further, as the optical fiber unit or the like is pressurefed, the lubricant is removed gradually from an inlet having a higherchance of contact and its vicinity area so that the pressure feedingproperty drops with time. Depending on the kind of the surface-coatingmaterial for the optical fiber unit, the coating of the inner wall ofthe pipe with the lubricant cannot bring about any advantage, leading tothe problem that the optical fiber unit or the like cannot be advanced.

The resin compositions according to the present invention can overcomethe problems described above. Examples of extremely valuable productsmaking use of the resin compositions according to this invention includepressurized air carrying optical fiber feeding pipes having a layer ofone of the resin compositions of this invention on at least inner wallsthereof as well as optical fiber units having a layer of one of theresin compositions according to this invention on at least outermostlayers thereof. This will be substantiated in Examples to be describedsubsequently.

In the present invention, the above feeding pipes can each be formedwith a desired cross-sectional shape from one of the resin compositionsof this invention by a forming process such as extrusion. On the otherhand, the above optical fiber units can each be produced by forming acoating layer of one of the resin compositions of this invention on acore by extrusion coating or the like. The coating layer generally has athickness in a range of from 0.2 mm to 5 mm.

The present invention will hereinafter be described specifically in thefollowing Examples. It is to be noted that the present invention is notlimited to these Examples.

In the Examples and Comparative Examples, various tests were carried outby the following methods.

(1) Abrasion resistance and lubricity

In each of the Examples and Comparative Examples, a resin compositionproduced therein was extruded into a hollow cylindrical body of 25.6 mmin outer diameter and 20.00 mm in inner diameter by an extruder. Thehollow cylindrical body was cut in lengths of 15.0 mm each to providetest pieces. An abrasion test was conducted using a Suzuki abrasiontester. Using as a counterpart material a material of the same materialas each test piece, the abrasion test was conducted under the followingtesting conditions--testing speed: 500 mm/sec, testing load: 500 gf, andtesting distance: 3 km. A weight change of the test piece before andafter the test was determined. The abrasion resistance of the test piecewas evaluated using the weight loss as an abrasion wear. At the sametime, the coefficient of friction of each test piece was measured toevaluate its lubricity.

(3) Tensile strength at yield point

The tensile strength at yield point of each of the produced resincompositions was measured in accordance with the procedures specifiedunder JIS K7113.

Examples 1-8 and Comparative Examples 1-5

In each of the Examples and Comparative Examples, "NEOZEX-2015M" (tradename; product of Mitsui Petro-chemical Industries, Ltd.), which islinear low-density polyethylene having an average molecular weight of100,000 (hereinafter abbreviated as "LLDPE"), and an organopolysiloxane(hereinafter abbreviated as "OP--Si") were mixed in the respectiveproportions shown in Table 1 in a Henschel mixer, followed by meltingand kneading at 220° C. In the table, "OP--Si (a)" indicates anorganopolysiloxane having an average molecular weight of 450,000 and avinyl group content of 0.004 wt. %, "OP--Si (b)" an organopolysiloxanehaving an average molecular weight of 350,000 and a vinyl group contentof 0.003 wt. %, and "OP--Si (c)" an organopolysiloxane having an averagemolecular weight of 50,000 and a vinyl group content of 0.01 wt. %.

Incidentally, the term "average molecular weight" as used herein means aweight average molecular weight irrespective of the resin unlessotherwise specifically indicated.

The resulting polymer blend and "HIGHZEX" (trade mark; product of MitsuiPetrochemical Industries, Ltd.), which is high-density polyethylenehaving an average molecular weight of 150,000 (hereinafter abbreviatedas "HDPE"), were then melted and kneaded at 220° C., so that anethylene-base resin containing the linear low-density polyethylene(LLDPE) and the high-density polyethylene (HDPE) in the respectiveproportions (wt. %) shown in Table 1 was formed and theorganopolysiloxane (OP--Si) was contained in the proportion (parts byweight) shown in Table 1 per 100 parts by weight of the ethylene-baseresin.

With respect to the resin composition so produced, the lubricity,abrasion resistance and tensile strength at yield point were measured.The results are also presented in Table 1.

                                      TABLE 1                                     __________________________________________________________________________    Example or                                                                            LLDPE                                                                              HDPE PP    OP-Si        Coefficient                                                                         Abrasion wear                                                                         Tensile strength           Comp. Ex. No.                                                                         (wt. %)                                                                            (wt. %)                                                                            (wt. parts)                                                                         (a)/(b)/(c)                                                                          wt. parts                                                                           of friction                                                                         (mg)    at yield point                                                                (kg/cm.sup.2)              __________________________________________________________________________    Example                                                                       1       10   90   --    (a)    0.5   0.14  0.3     210                        2       10   90   --    (a)    2.5   0.09  0.2     200                        3       10   90   --    (a)    7.2   0.08  0.1     190                        4       10   90   --    (a)    15.3  0.05  0.1     170                        Comp. Ex.                                                                     1       10   90   --    (a)    0.05  0.48  0.9     210                        2       10   90   --    --     --    0.55  1.2     220                        3       10   90   --    (a)    35.0  0.05  0.1     90                         Example                                                                       5       10   90   --    (b)    0.5   0.15  0.4     210                        Comp. Ex.                                                                     4       10   90   --    (c)    0.5   0.52  0.8     160                        Example                                                                       6       50   50   --    (a)    0.5   0.10  0.1     160                        7       100  0    --    (a)    0.5   0.10  0.1     110                        8       6    94   --    (a)    0.5   0.16  0.3     220                        Comp. Ex.                                                                     5       0    100  --    (a)    0.5   0.35  0.8     220                        __________________________________________________________________________

From Table 1, the following advantages of the present invention can beenvisaged:

(i) As is substantiated through a comparison between Examples 1-4 andComparative Examples 1-3, addition of an organopolysiloxane having ahigh molecular weight in a proportion outside a specific range is unableto obtain a resin composition excellent in balance among variousphysical properties such as coefficient of friction, abrasion wear andtensile strength at yield point.

(ii) As is substantiated through a comparison between Example 5 andComparative Example 4, an organopolysiloxane cannot contribute to animprovement especially in lubricity unless it has a high molecularweight in a particular range.

(iii) As is substantiated, for example, through a comparison betweenComparative Example 5 and Example 1, advantages available from the useof low-density polyethylene are exhibited as extremely high lubricityand abrasion resistance.

The above-described differences in effects may be attributable primarilyto the possibility that, in each resin composition according to thepresent invention, the added organopolysiloxane of the high molecularweight is dispersed uniformly as very small particles in thehigh-density polyethylene under the action of the linear low-densitypolyethylene whereas, in the resin composition of Comparative Example 5,the organopolysiloxane is not fully dispersed in the high-densitypolyethylene and is contained as coarse particles of a considerable sizethere.

Examples 9-13

Resin compositions were obtained as in Examples 1, 5, 6, 7 and 8,respectively, except that, upon melting and kneading the linearlow-density polyethylene (LLDPE) and the organopolysiloxane (OP--Si), anorganic peroxide [1,3-bis-(t-butylperoxyisopropyl)benzene] was caused topresent in an amount of 0.004 part by weight per 100 parts by weight ofthe linear low-density polyethylene (LLDPE).

With respect to the resin compositions so produced, the lubricity,abrasion resistance and tensile strength at yield point were measured.The results are also presented in Table 2.

                                      TABLE 2                                     __________________________________________________________________________    Example                                                                            LLDPE                                                                              HDPE PP    OP-Si     Coefficient                                                                         Abrasion wear                                                                         Tensile strength at              No.  (wt. %)                                                                            (wt. %)                                                                            (wt. parts)                                                                         (a)/(b)                                                                           wt. parts                                                                           of friction                                                                         (mg)    yield point                      __________________________________________________________________________                                                 (kg/cm.sup.2)                    9    10   90   --    (a) 0.5   0.09  0.1     190                              10   10   90   --    (b) 0.5   0.10  0.2     190                              11   50   50   --    (a) 0.5   0.09  0.1     160                              12   100  0    --    (a) 0.5   0.09  0.1     110                              13   6    94   --    (a) 0.5   0.10  0.1     220                              __________________________________________________________________________

Examples 14-21

In each Example, "TOKUYAMA POLYPRO MJ160" (trade name; product ofTokuyama Soda Co., Ltd; hereinafter abbreviated as "PP".) was used as apropylene-base resin. PP and the organopolysiloxane (OP--Si) shown inTable 3 were mixed in a Henschel mixer, followed by melting and kneadingat 220° C.

The resulting polymer blend as well as the linear low-densitypolyethylene (LLDPE) and the high-density polyethylene (HDPE), both usedin Example 1, were then melted and kneaded at 220° C., so that anethylene-base resin containing the linear low-density polyethylene(LLDPE) and the high-density polyethylene (HDPE) in the respectiveproportions (wt. %) shown in Table 3 was formed, the polypropylene (PP)was contained in the proportion (parts by weight) shown in Table 3 per100 parts by weight of the ethylene-base resin, and theorganopolysiloxane (OP--Si) was contained in the proportion (parts byweight) shown in Table 1 per 100 parts by weight of the sum of theethylene-base resin and the polypropylene (PP).

With respect to the resin composition so produced, the lubricity,abrasion resistance and tensile strength at yield point were measured.The results are also presented in Table 3.

                                      TABLE 3                                     __________________________________________________________________________    Example                                                                            LLDPE                                                                              HDPE PP    OP-Si     Coefficient                                                                         Abrasion wear                                                                         Tensile strength at              No.  (wt. %)                                                                            (wt. %)                                                                            (wt. parts)                                                                         (a)/(b)                                                                           wt. parts                                                                           of friction                                                                         (mg)    yield point                      __________________________________________________________________________                                                 (kg/cm.sup.2)                    14   10   90   0.5   (a) 0.5   0.12  0.3     220                              15   10   90   5.0   (a) 0.5   0.12  0.3     230                              16   10   90   15.0  (a) 0.5   0.12  0.3     240                              17   10   90   50.0  (a) 0.5   0.15  0.4     300                              18   10   90   0.5   (b) 0.5   0.12  0.3     220                              19   50   50   0.5   (a) 0.5   0.10  0.1     200                              20   100  0    0.5   (a) 0.5   0.10  0.1     160                              21   6    94   0.5   (a) 0.5   0.16  0.3     220                              __________________________________________________________________________

Examples 22-28

Resin compositions were obtained as in Examples 14, 15, 16, 18 and 21,respectively, except that, upon melting and kneading the polypropylene(PP) and the organopolysiloxane (OP--Si), an organic peroxide[1,3-bis-(t-butylperoxyisopropyl)benzene] was caused to present in anamount of 0.004 part by weight per 100 parts by weight of thepolypropylene (PP).

With respect to the resin compositions so produced, the lubricity,abrasion resistance and tensile strength at yield point were measured.The results are also presented in Table 4.

                                      TABLE 4                                     __________________________________________________________________________    Example                                                                            LLDPE                                                                              HDPE PP    OP-Si     Coefficient                                                                         Abrasion wear                                                                         Tensile strength at              No.  (wt. %)                                                                            (wt. %)                                                                            (wt. parts)                                                                         (a)/(b)                                                                           wt. parts                                                                           of friction                                                                         (mg)    yield point                      __________________________________________________________________________                                                 (kg/cm.sup.2)                    22   10   90   0.5   (a) 0.5   0.10  0.1     210                              23   10   90   0.5   (a) 1.0   0.09  0.1     210                              24   10   90   0.5   (a) 5.0   0.08  0.1     190                              25   10   90   5.0   (a) 0.5   0.10  0.1     210                              26   10   90   15.0  (a) 0.5   0.10  0.1     230                              27   10   90   0.5   (b) 0.5   0.10  0.1     210                              28   6    94   0.5   (a) 0.5   0.10  0.1     210                              __________________________________________________________________________

Examples 29-36 and Comparative Examples 6-9

As products making use of resin compositions according to the presentinvention, optical fiber feeding pipes were produced. In each of theExamples and Comparative Examples, the resin composition shown in Table5 was produced. After the resin composition was kneaded in an extruder,it was extruded into an optical fiber feeding pipe having an innerdiameter of 6 mm and an outer diameter of 8 mm. In Table 5, theorganopolysiloxane (OP--Si) is the same as the organopolysiloxaneemployed in Example 1, that is, the organopolysiloxane having theaverage molecular weight of 450,000 and the vinyl group content of 0.004wt. % [i.e., OP--Si (a)]. The other components, LLDPE, HDPE and PP areas specified above.

In Table 5, Comparative Example 7, HDPE was added with 0.1 wt. % ofoleic azide (lubricant) in place of OP--Si. Comparative Example 8 isdirected to a HDPE pipe whose inner wall was coated with oleic azide(lubricant).

Various properties of the optical fiber feeding pipes so produced arealso shown in Table 5. The properties set out in Table 5 were determinedas will be described below.

(1) Coefficient of friction:

Each feeding pipe was wound three times around a drum having a diameterof 60 cm. An optical fiber unit having an inner diameter of 2 mm andcoated with foamed polyethylene was inserted into the pipe. Whileapplying a back tension of 40 g to the leading end of the optical fiber,the optical fiber was pulled out. The coefficient of friction of thefeeding pipe was calculated from the tensile force required upon pullingout the optical fiber.

(2) Pressure feed performance:

Pressurized dry air was blown at 6 kg/cm² into each feeding pipe of1,000 m in length. The pressure feed performance of the feeding pipe wasevaluated in term of the time (minutes) required to pressure feed anoptical fiber unit forward through the feeding pipe. In Table 6, (1)indicates pressure feed performance under linear conditions while (2)designates pressure feed performance when the feeding pipe was woundaround a drum having a diameter of 1 m.

(3) Impact resistance:

A 1-kg weight having a striking face of 25 mm in diameter was caused todrop onto each feeding pipe at 25° C. from a height of 0.5 m. The impactresistance of the feeding pipe was evaluated in accordance with thefollowing evaluation standard:

Good . . . No damage.

Fair . . . Some cracks occurred but posed no problem or inconvenience inpractice.

Poor . . . Cracks propagated to the inner wall of the pipe so thatpressurized carrying air leaked through the cracks. The pipe was nolonger usable.

(4) Formability:

Each resin composition was extruded at a resin temperature of 170°-190°C. into a hollow cylindrical shape of 8 mm in outer diameter and 6 mm ininner diameter. The formability of the resin composition was evaluatedin accordance with the following evaluation standard.

Excellent . . . Pipes of 10,000 m or longer were successfully extrudedwithout problem.

Good . . . Pipes of at least 5,000 m but not longer than 10,000 m weresuccessfully extruded.

Fair . . . Pipes of at least 2,000 m but not longer than 5,000 m weresuccessfully extruded.

Poor . . . Pipes of 1,000 m or shorter were only extruded.

                                      TABLE 5                                     __________________________________________________________________________           LLDPE                                                                              HDPE PP    OP-Si Coefficient of                                                                        Pressure feed performance                                                                    Impact                           (wt. %)                                                                            (wt. %)                                                                            (wt. parts)                                                                         (wt. parts)                                                                         friction (μ)                                                                       (1)     (2)    resistance                                                                         Formability          __________________________________________________________________________    Example 29                                                                           10.0 90.0 --    0.50  0.08    42 min  51 min Good Excellent            Example 30                                                                           10.1 89.9 --    1.01  0.07    25 min  33 min Good Excellent            Example 31                                                                           10.2 89.8 --    2.04  0.05    25 min or less                                                                        30 min or less                                                                       Good Excellent            Example 32                                                                           10.5 89.5 --    5.26  0.05    25 min or less                                                                        30 min or less                                                                       Good Good                 Example 33                                                                           11.1 88.9 --    11.11 0.05    25 min or less                                                                        30 min or less                                                                       Good Good                 Example 34                                                                           11.8 88.2 --    17.65 0.05    25 min or less                                                                        30 min or less                                                                       Good Fair                 Example 35                                                                           100  --   --    1.01  0.07    25 min  33 min Fair Fair                 Example 36                                                                           10.2 89.8 0.51  1.02  0.05    25 min or less                                                                        33 min or less                                                                       Good Excellent            Comp. Ex. 6                                                                          --   100  --    --    0.2     Stopped at                                                                            Stopped at                                                                           Good Excellent                                                 100-200 m                                                                             100 m or less                    Comp. Ex. 7                                                                          --   *100 --    --    0.15    60 min or more                                                                        Stopped at                                                                           Good Excellent                                                         800 m or less                    Comp. Ex. 8                                                                          --   100  --    --    0.15    750 min or less                                                                       Stopped at                                                                           Good Excellent                                                         500 m or less                    Comp. Ex. 9                                                                          --   100  --    1.01  0.07    --      --     Poor Poor                 __________________________________________________________________________     *Lubricant (0.1 wt. %) was contained.                                    

We claim:
 1. An optical fiber feeding pipe comprising a resincomposition formed on at least an inner wall thereof, said resincomposition having excellent surface lubricity, mechanical strength andabrasion resistance, and being useful in mechanical parts where goodlibricity is required, consisting essentially of a mixture of:100 partsby weight of an ethylene-base resin comprising at least 2 wt. % oflinear low-density polyethylene; and 0.1-30 parts by weight of anorganopolysiloxane having a weight average molecular weight of at least300,000.
 2. An optical fiber unit comprising a layer of a resincomposition formed on at least an outermost layer thereof, said resincomposition having excellent surface lubricity, mechanical strength andabrasion resistance, and being useful in mechanical parts where goodlubricity is required, consisting essentially of a mixture of:100 partsby weight of an ethylene-base resin comprising of least 2 wt. % oflinear low-density polyethylene; and 0.1-30 parts by weight of anorganopolysiloxane having a weight average molecular weight of at least300,000.
 3. An optical fiber feeding pipe comprising a resin compositionformed on at least an inner wall thereof, said resin composition havingexcellent surface lubricity, mechanical strength and abrasionresistance, and being useful in mechanical parts where good lubricity isrequired, consisting essentially of a mixture of:100 parts by weight ofan ethylene-base resin comprising at least 2 wt. % of linear low-densitypolyethylene; 0.1-100 parts by weight of a propylene-base resin; and0.1-30 parts by weight, per 100 parts by weight of the sum of theethylene-base resin and the propylene-based resin, of anorganopolysiloxane having a weight average molecular weight of at least300,000.
 4. An optical fiber unit comprising a layer of a resincomposition formed on at least an outermost layer thereof, said resincomposition having excellent surface lubricity, mechanical strength andabrasion resistance, and being useful in mechanical parts where goodlubricity is required, consisting essentially of a mixture of:100 partsby weight of an ethylene-base resin comprising at least 2 wt. % oflinear low-density polyethylene; 0.1-100 parts by weight of apropylene-base resin; and 0.1-30 parts by weight, per 100 parts byweight of the sum of the ethylene-base resin and the propylene-basedresin, of an organopolysiloxane having a weight average molecular weightof at least 300,000.
 5. An optical resin fiber feeding pipe according toclaim 1, wherein the content of vinyl groups in the organopolysiloxaneis in a range of 0.001-0.3 wt. %.
 6. An optical fiber unit according toclaim 2, wherein the content of vinyl groups in the organopolysiloxaneis in a range of 0.001-0.3 wt. %.
 7. An optical fiber feeding pipeaccording to claim 3, wherein the content of vinyl groups in theorganopolysiloxane is in a range of 0.001-0.3 wt. %.
 8. An optical fiberunit according to claim 4, wherein the content of vinyl groups in theorganopolysiloxane is in a range of 0.001-0.3 wt. %.